The electrostatic charge image developing toner is used for image formation in which an electrostatic charge image is visualized in a printer, a copying machine, a facsimile, or the like. Taking the image formation by the electrophotographic method as an example, the image formation is performed by in such a manner that, first, an electrostatic latent image is formed on a photosensitive drum, which is then developed with a toner, transferred to transfer paper or the like, and fixed by heat or the like.
As the electrostatic charge image developing toner, for example, a toner in which a solid fine particle such as silica is attached to the surface as an external additive is generally used for the purpose that a charge control agent, a release agent, a magnetic material, and the like are dry-mixed in a binder resin and a colorant, as necessary, and then various performances such as fluidity are imparted to toner particles obtained by melt kneading with an extruder or the like, followed by pulverization and classification, a so-called melt-kneading pulverization method.
Further, according to the recent demands for high definition, production methods such as a suspension polymerization method, an emulsion aggregation method, a dissolution suspension method and the like, which are easy to control the particle diameter and particle size distribution of the toner, have been proposed.
In recent years, efforts to apply images obtained by electrophotographic method such as copying machines and printers to the professional field are actively conducted, and it has been necessary to beautifully output images such as photographs and graphics from the purpose of printing characters so far. For this reason, it is strongly desired that the output image has a higher quality image and higher glossiness than ever.
Since the electrophotographic apparatus is expected to simultaneously achieve low energy consumption and high-speed printing, the toner is strongly desired to be melted with low heat energy (time×temperature) and fixed on a medium, the excellent fixability at a low temperature is in an antinomic relation with the blocking resistance, and both of them are desired to be achieved. Various investigations have been performed so as to realize both of the excellent fixability at a low temperature and the blocking resistance.
On the other hand, with regard to the fixing temperature at the time of image output by the electrophotographic apparatus, the actual fixing temperature is not a constant value, but there is some nonuniformity. For example, when the image is output immediately after the power is turned on, the fixing temperature becomes low, but when continuous printing is performed from there, the fixing temperature becomes high. In addition, when the toner layer is thick (for example, toners of a plurality of colors are printed densely), the actual temperature applied to the toner layer is low, and when the toner layer is thin (for example, toners of a single color are printed thinly), the actual temperature applied to the toner layer is high.
In recent years, frequency of control of a fixing temperature of a heat roller has been reduced to reduce energy, so nonuniformity of the fixing temperature is easy to occur. When the fixing temperature is high, there arises a problem that hot offset (a phenomenon in which the toner on a transfer material adheres to a fixing member and then the toner transfers to the transfer material again to contaminate the transfer material) occurs. Therefore, a toner having good fixability even on a high temperature side is desired.
PTL 1 discloses a toner containing a crystalline polyester resin and a release agent, in which a structure in which the crystalline polyester resin is in contact with the releasing agent is present on a cross section of the toner dyed with ruthenium, and when a cross-sectional area for the structure is set as A, a cross-sectional area only for the release agent is set as B, and a cross-sectional area only for the crystalline polyester resin is set as C, relationships represented by 40≤100×A/(A+B+C)≤70, 10≤100×B/(A+B+C)≤30, and 20≤100×C/(A+B+C)<30 are satisfied, fixability is less dependent on the fixing temperature, and a heat storage property is excellent.
PTL 2 proposes an electrostatic charge image developing toner containing a crystalline organic compound having a melting point of 50° C. to 150° C. as a fixing assistant for the purpose of heat resistant storage and low temperature fixing, in which in order to compatibilize a resin and the fixing assistant at the time of heating, in DSC measurement of toner, the amount of heat absorption at the melting maximum value derived from the fixing assistant at second temperature rise becomes smaller than that at first temperature rise, a glass transition temperature of the toner is more decreased than that the glass transition temperature of the resin, and the glass transition temperature at the second temperature rise becomes lower than that at the first temperature rise.
PTL 3 discloses an electrostatic charge image developing toner which is a core shell structure including a toner base particle and a shell layer, in which the toner base particle includes a resin coating layer formed of a water soluble resin on a surface of the toner base particle, and the shell layer on the resin coating layer.
PTL 4 proposes an electrostatic charge image developing toner which is a core shell structure including a toner base particle and a shell layer, in which a storage modulus (G′) of a toner by a dynamic viscoelasticity test is adjusted in order to satisfy blocking resistance, excellent fixability at low temperature, and offset resistance.